From c2a880c290dba8dd57f5384664bd52945574d845 Mon Sep 17 00:00:00 2001
From: Danny Robson <danny@nerdcruft.net>
Date: Tue, 6 Mar 2018 13:53:39 +1100
Subject: [PATCH] matrix: fix missed negation on one component of ortho

---
 matrix.cpp | 20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/matrix.cpp b/matrix.cpp
index 8af742d4..5e964787 100644
--- a/matrix.cpp
+++ b/matrix.cpp
@@ -133,19 +133,19 @@ matrix<Rows,Cols,T>::is_affine (void) const
 //-----------------------------------------------------------------------------
 template <typename T>
 util::matrix4<T>
-util::ortho (T left,   T right,
-             T bottom, T top,
-             T near,   T far)
+util::ortho (T l, T r, // left, right
+             T b, T t, // bottom, top
+             T n, T f) // near, far
 {
-    CHECK_GT (far, near);
+    CHECK_GT (f, n);
 
-    T tx = - (right + left) / (right - left);
-    T ty = - (top + bottom) / (top - bottom);
-    T tz = - (far + near)   / (far - near);
+    T tx = - (r + l) / (r - l);
+    T ty = - (t + b) / (t - b);
+    T tz = - (f + n) / (f - n);
 
-    T rl = 2 / (right - left);
-    T tb = 2 / (top - bottom);
-    T fn = 2 / (far - near);
+    T rl =  2 / (r - l);
+    T tb =  2 / (t - b);
+    T fn = -2 / (f - n);
 
     return {{
         { rl,  0,  0, tx },